1. Field of the Invention
The present invention relates to a vehicle mounted spraying system and a method of accurately controlling the point of application, spray pattern and area of coverage by use of a solid stream producing nozzle to direct the flow of the product being dispensed. More particularly the apparatus includes a pump for discharging the product, the pump being driven at a speed correlated to the ground speed of the vehicle and responsive to a setable product application rate. The product is delivered through a novel discharge nozzle so as to maintain a constant solid stream spray pattern and density of product applied to a surface, irrespective of the vehicle speed. A fluid pressure responsive variable orifice discharge nozzle is utilized to produce a solid stream of product which may be precisely aimed and projected in such a manner as to provide preset uniform coverage for a wide area beyond the lane of traffic occupied by the vehicle and over a wide range of vehicle speeds and product application rates.
2. Description of the Prior Art
Vehicle mounted spray systems for applying fluid products to road or ground surfaces are well known in the prior art including various devices for synchronizing the application rate and spray pattern of a fluid with the speed of the vehicle upon which the system is mounted. Systems of this type, however, normally utilize fixed orifice spray nozzles which impose severe limitations on the operating ground speed range at which the chosen product application rate can be suitably maintained. If the operating ground speed at which spaying is to be accomplished is 50 miles per hour for instance, the minimum speed at which suitable product application at any chosen application rate per lane mile could be expected would be approximately 25 miles per hour. If a different product application rate is desired it is, of course, necessary to replace all of the fixed orifice nozzles to attain the new application rate for the stated speed range.
Since the nozzle pressure for any given size orifice increases by the square of the ground speed increase, a nozzle capable of maintaining a given spread rate at a low ground speed becomes inoperative at higher speeds because of the exponentially increased nozzle pressures. As an example, the following chart shows the nozzle pressure characteristic of a 0.016" orifice set for a spread rate of 30 gallons per lane mile (GPLM):
______________________________________ Nozzle Ground Speed Nozzle Orifice Flow Rate MPH PSI GPM ______________________________________ 1 20 1/8 2 80 1/4 4 320 1/2 8 1,280 1 16 5,120 2 32 20,480 4 64 81,920 8 ______________________________________
If the spread rate is increased to 60 GPLM for the same size orifice, the following pressures result:
______________________________________ Nozzle Ground Speed Nozzle Orifice Flow Rate MPH PSI GPM ______________________________________ 1 80 1/4 2 320 1/2 4 1,280 1 8 5,120 2 16 20,480 4 32 81,920 8 64 327,680 16 ______________________________________
as these figures demonstrate, the nozzle pressures for a fixed orifice capable of operating at low speeds become prohibitively high at higher speeds.
For effective roadway spraying the system must operate over a very wide range of ground speeds e.g. 0-50 mph, as for instance between an intersection and open road. Fixed orifice nozzle systems for roadway spraying are thus generally inadequate because of the limited ground speed spraying range and the necessity for changing multiple nozzles when a different spread rate is desired.
In most prior art systems, a fluid pump for delivering the liquid product is normally driven by some form of motor means such as an hydraulic or electrical motor, or an internal combustion engine with various known means being utilized to control the speed of the pump drive motor relative to the ground speed of the vehicle in order to maintain a constant ratio, determined by the desired product spread rate. Thus, the amount of product delivered is increased in correlation to the increased speed of the vehicle to maintain the chosen spread rate. U.S. Pat. No. 4,019,685 to Tangeman et al shows such a system wherein the correlation between vehicle ground speed and the volume of liquid product delivered is accomplished with a fully mechanical control device specifically involving a cam-type drive apparatus. Although the Tangemen et al disclosure does not include the description of a liquid spray nozzle system for dispensing the liquid product, fixed orifice nozzles are usually utilized to apply the product. The product is applied directly to the ground or road surface in a vertical direction, either from the front or rear end of the vehicle, in an atomized spray pattern with the limitations discussed.
U.S. Pat. No. 4,817,870 to Dalton discloses a system for maintaining a constant application rate by automatically controlling the discharge rate of a liquid product delivery pump utilizing an electronic control apparatus. The control apparatus automatically adjusts the drive ratio of a hydrostatic transmission in response to operator-selected changes in the length of the spray bar. The Dalton patent illustrates the typical vertically directed, fixed orifice spray nozzle arrangement. A plurality of nozzles are typically arranged on a transverse spray bar. The main spray bar covers the travel lane of the vehicle and additional spray bars extend laterally to cover additional areas on each side of the vehicle.
In addition to the speed synchronized spray applicators discussed, U.S. Pat. No. 3,344,993 to Wilder et al discloses an additional feature wherein the size of the spray nozzle orifice is controlled responsive to the delivery pump speed and quantity of product delivered. Thus, as the line pressure increases the orifice size increases. A uniform product spray rate or pattern results since the velocity of the material discharged at the orifice also increases with ground speed to increase the nozzle flow rate. In this patent, the nozzle opening or orifice is controlled by a mechanical linkage which is responsive to a bellows device subject to the fluid pressure in the product delivery line. The type of nozzle used in the Wilder et al patent is a simple orifice and deflection plate which directs the fluid product downwardly onto the traveled surface directly in the rear of the vehicle. The nozzle of the Wilder et al device, however, is a mechanically operated rotary regulator which produces an atomized discharge, such as used to spray a liquid onto a particulate base. The orifice configuration is not designed for high pressure, high speed spraying or to produce a high pressure solid stream liquid spray at any speed. Additionally, this device depends upon a mechanical linkage for operating each individual nozzle regulator. The exposed mechanical linkage is therefor subject to frequent damage and malfunction in a hostile environment. With this arrangement, a malfunction in the linkage of only one nozzle has the potential of affecting all nozzles since they are connected to a common mechanical operator link or bar.
The patent to Broderson U.S. Pat. No. 3,529,772 discloses a speed compensated water sprinkler system for water tank vehicles utilizing an adjustable spray nozzle which produces a wide-arc horizontal spray. A spring biased deflector plate operates to vary the size of the sprinkler orifice in proportion to the pressure of the water supply. In this manner not only the pattern covered by the water spray but also the density of the water applied to the ground remain substantially constant within a designed speed range of the vehicle. In the Broderson system, either a hydraulic motor, an internal combustion engine or an electrical motor, the speed of which is controlled responsive to the vehicle ground speed, is used to vary the output of the delivery pump for the sprayed product.
The following listed patents all disclose various means of controlling the output of fixed orifice discharge nozzles by controlling the quantity and pressure of the liquid product delivered to the fixed nozzle.
______________________________________ U.S. Pat. No. Patentee ______________________________________ 3,233,832 Hallberg 3,670,962 Johnston 4,322,034 Fox 5,035,357 Breckell et al ______________________________________